The gene bric a brac (bab) is a transcriptional regulator that is required for the proper development of the ovary, leg and antenna in Drosophila melanogaster. Our long term goal is to have a molecular understanding of how bab functions, and to use bab as an entryway to the investigation of limb and ovary development. We propose to continue our studies by means of the following specific aims: 1. A functional analysis of bab. We have extensive knowledge of the gene structure, genetics and expression pattern of bab. We have identified a target gene for bab (it binds its own locus) and shown that bab can repress its own production. Our current goal is to understand how bab functions at a molecular level. To this we will investigate the consequence of babII protein binding to a promoter. In addition, we will do structure/function analysis of the babII protein, investigating the function of the BTB domain and psq motif. 2. A screen for genes that interact with bab during leg development. bab provides a unique tool in understanding the process of pattern formation in the leg of Drosophila, with specific interest in the formation of the proximal-distal axis. bab is required to give the three central segments of the tarsus their identity, therefore the gene must be involved in the process of interpreting positional cues along the axis. Understanding how bab interacts with other genes to interpret positional information will give insight into the molecular mechanism of proximal- distal axis formation. Using a genetic approach, we will identify genes that interact with bab. These genes will be studied to determine their role in leg development. 3. A genetic and molecular characterization of the ntf (no terminal filaments) gene. We have recently identified that ntf gene, the second gene identified (in addition to bab) that is required for terminal filament formation. Our long term goal is to understand how developmental processes work during ovary development. We are taking a genetic approach to this goal, identifying genes that are required for ovary development and then analyzing these genes. Analysis of bab has told us a great deal about ovary development, the molecular and genetic characterization of the ntf gene should be just as informative.